.TH std::countl_zero 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::countl_zero \- std::countl_zero

.SH Synopsis
   Defined in header <bit>
   template< class T >                         \fI(since C++20)\fP
   constexpr int countl_zero( T x ) noexcept;

   Returns the number of consecutive 0 bits in the value of x, starting from the most
   significant bit ("left").

   This overload participates in overload resolution only if T is an unsigned integer
   type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned
   long long, or an extended unsigned integer type).

.SH Parameters

   x - value of unsigned integer type

.SH Return value

   The number of consecutive 0 bits in the value of x, starting from the most
   significant bit.

.SH Notes

   Feature-test macro  Value    Std      Feature
   __cpp_lib_bitops   201907L (C++20) Bit operations

.SH Example


// Run this code

 #include <bit>
 #include <bitset>
 #include <cstdint>
 #include <iostream>

 int main()
 {
     for (const std::uint8_t i : {0, 0b11111111, 0b11110000, 0b00011110})
         std::cout << "countl_zero( " << std::bitset<8>(i) << " ) = "
                   << std::countl_zero(i) << '\\n';
 }

.SH Output:

 countl_zero( 00000000 ) = 8
 countl_zero( 11111111 ) = 0
 countl_zero( 11110000 ) = 0
 countl_zero( 00011110 ) = 3

.SH See also

   countl_one  counts the number of consecutive 1 bits, starting from the most
   (C++20)     significant bit
               \fI(function template)\fP
   countr_zero counts the number of consecutive 0 bits, starting from the least
   (C++20)     significant bit
               \fI(function template)\fP
   countr_one  counts the number of consecutive 1 bits, starting from the least
   (C++20)     significant bit
               \fI(function template)\fP
   popcount    counts the number of 1 bits in an unsigned integer
   (C++20)     \fI(function template)\fP
   all         checks if all, any or none of the bits are set to true
   any         \fI(public member function of std::bitset<N>)\fP
   none
